WCAG 2.1 - SC 1.3.2 Meaningful Sequence

It is important that it be possible to programmatically determine at least one sequence of the content that makes sense. Content that does not meet this Success Criterion may confuse or disorient users when assistive technology reads the content in the wrong order, or when alternate style sheets or other formatting changes are applied.

Official Requirements:

1.3.2 Meaningful Sequence: When the sequence in which content is presented affects its meaning, a correct reading sequence can be programmatically determined. (Level A)

How to fix:

• If using a table for layout, make sure the content within it makes sense when linearized.
• Use structural markup to make sure all elements make sense when viewed in source order, and CSS to create a visual presentation.